Fluorescent sign lamp



ug. 29, 1950 P. sERl-:No 2,520,513

FLUoREscENT SIGN LAMP Filed April 20. 1949 Patented Aug. 29, 1950 UNITEDSTATES 4rui'lsin OFFICE l. This invention relates to signs, and, moreparticularly, is concerned with fluorescent S1211 lamps.

Even more specically, the present invention pertains to thattype offluorescent sign lamp wherein the sign comprises a plurality of letters,characters and/or symbols (all hereinafter reicrred to as characters)fashioned from iluorescent material and carried by an elongated plate ofinsulating material which is located within a transparent tube. The tubeis filled with rareed gases and is arranged to passl an electricdischarge which activates thefiuorescent malterial of the characters.Signs of this type conventionally have the characters formed by tracingthe same with fluorescent powders on the elongated plate.

In present-day manufacture of signs of the character described. manydiiiculties are present which have made the signs delicate, expensiveand complicated. The principal difiiculties have been: failure to obtaina clean and uniform tracing of the characters on the elongated plate,unsatisfactory mounting of the elongated plate in the transparent tube,special care in handling the various components during manufacture,inability to secure a simple and ilrm assembly of the parts in thecompleted sign, and complicated devices to direct the electricaldischarge and obtain a sufilcient intensity of light emanation from theuorescing characters.

It is an object of my invention to provide fluorescent sign lamp whereinthe foregoing diilloulties are overcome.

It is a more speciiic object of my invention to provide a fluorescentsign lamp of the character described in which the characters can betraced quickly and easily -by lling in shallow depressions of properoutline so that the finished characters are clean and uniform.

It is another specific object of my invention to provide a fluorescentsign lamp of the character described wherein the plate is indirectlysupported by the tube thereby to obtain a iirm and qiuckly assembledplate mounting which will not cause breakage of the fragile tube andplate during either construction or use.

It is another specific object of my invention to provide a iiuorescentsign lamp of the chan acter described wherein the plate mountingconstitutes resilient members and cushions so that, although themounting is firm, the plate, nevertheless, will not exert any sudden orsubstantial pressure against the tube.

It is another specinc object of my invention to provide a fluorescentsign lamp of the character described wherein the plate is so positionedin the tube that the full electrical discharge passes in front of theplate so that a hitherto unobtained degree of brilliance is attained bythe fluorescent characters. l l

Other objects of my invention will in part be oittious and in part willbe pointed out hereina r.

My invention accordingly consists in the features of construction,combinations of elements and arrangements of parts which will beexemplified in the constructions hereinafter described and illustratedand of which the scope of application will be indicated in the appendedclaims.

In the accompanying drawings in which are shown various possibleembodiments of my invention,

Fig. 1 is a front view of a iiuorescent sign lamp constructed inaccordance with my invention;

Fig. 2 is an enlarged axial section through one of the ends of the signin a plane perpendicular to the character-carrying plate;

Figs. 3 and 4 are sectional views taken substantially along the line 3 3and 4 4, respectively, of Fia. 2;

`Iiig. 5 is a broken-away perspective view of the end of the sign shownin Fig. 2; and

Figs. 6 and 7 are transverse sectional views through ends of iluorescentsign lamps having modied forms of plate mountings embodying myinvention.

Referring now in detail to the drawings, and, more particularly. toFigs. 1 through 5, the reference numeral Iii denotes a fluorescent signlamp embodying my invention. Said lamp comprises an elongatedtransparent tube ii which, conventionally, is Vfabricated from glass andis of circular cross-section, it being understood that the particularconilguration of the cross-section can be varied to suit consumerdemand. Both ends of the tube are tapered to hermetically closed stemsil. The tube is evacuated 'through a stub i8 which subsequently issealed. Before sealing, however, the tube is charged at a conventionalpressure with one or more of the rare gases which commonly are used instandard uorescent lamps. By way oi example argon or krypton may beemployed at a pressure of between 0.5 to 2 mm. of mercury. In addition asmall amount of mercury vapor can be present.

At the ends of the tube I provide the usual electrodes il mounted onlead-in wires t-l! which are conventionally sealed in the stems. The

electrodes are shown as representative either of the "cold" electrodetype, operating with a nigh voltage drop and a high strikingvoltage, orof the oxide-coated heated electrode type, operating with a low voltagedrop and starting with a comparatively low striking voltage. As is wellunderstood. both types are suitable for the purpose of maintaining anelectric discharge in. an attenuated gas. For example, elongatedcylinders of nickel or iron, coated with barium oxide, may be used aselectrodes. The lead-in wires run to terminals 22 which, as illustrated,may be of the type adapted to be plugged in suitable sockets. Energy issupplied to the electrodes through any conventional circuit. The ends ofthe tube are housed in shells 2l which, conveniently, are made from aplastic, e. g. a phenol formaldehyde condensation resin. The tubes aresecured to the shell, for example by cement 26, and'openings areprovided for passage and support of the terminals 22.

Located within the tube I2 andextending over substantially its entirelength, is a plate 28 which, desirably, is made of an electricinsulating material, e. g. glass. The plate has a breadth which issomewhat smaller than the inside diameter of the tube. Pursuant to aprincipal feature of my invention, the plate is odset from thelongitudinal axis of the tube. In other` words, the plate, which is thinand has parallel, plane front and back surfaces, and, moreover, which isarranged with said surfaces parallel -to this axis of the tube, has itsfront surface spaced from said axis in a direction radially of the tubeand its rear surface located on the same side of, said axis. It is onthis front surface of the plate that the fluorescent characters arecarried, so that said characters face the major portion of the tubespace through which the electric discharge between the electrodespasses. I have found that such an arrangement results in an appreciableincrease in brilliance compared to an arrangement in all respectssimilar save for the aforesaid placement of the plate, such platesheretofore having been located so as to include the longitudinal axis ofthe tube.

Means is provided to hold the plate in its stated position. As shown inFigs. l through 5, said means comprises a spring plate ring 30cornpressed between the tube and the plate, one such ring being providedat each end of the plate. To avoid contact of the plate with the tube,each end of the plate is Wrapped in a ribbon 32 which is yielding and,preferably, is electrically nonconductive and a poor heat conductor.Examples of materials of ,this nature are asbestos and glass fiberribbons. By way of illustration, the ribbon is 20 mm. wide and about 2mm. thereof is permitted to extend beyond the edge of the plate. Oneturn with some overla-p (see Fig. is wrapped about each end of the platebefore the plate is inserted in the tube.

The ring 30 can be simply made from a fiat strip of spring steelprovided with a notch on each edge thereof near its ends. The notchesare on opposite longitudinal edges and have depths equal toapproximately half the width of the strip. The strip is bent to overlapits ends and register the notches, and' the latter are interengaged tofix the ring in an approximately circular shape. The ring then iscompressed and inserted between the tube and plate. Contact between thering and tube is avoided by wr'apping the junction of each ring with aribbon 34 similar to the ribbon 32 and placing said wrapped junctionadjacent the tube. After the ring is released, it will press itsassociated end of the plate against the tube and rmly and resilientlyhold it in position. -the ribbons serving to cushion any shockexperienced during assembly or use. A further advantage of thisconstruction is that it permits expansion of the parts during theheating incident to obtaining a vacuum, and also a1- lows largetolerances and slight movements of the parts without causing breakagebecause of the imposition of sudden or substantial stresses on thedelicate tube. Other rigid mounting systems that will not permitmovements, or will allow parts to come into contact atdifferent'temperatures or because of diiferent heat conductivitycharacteristics, will result in breakage.

The ring functions to hold the plate against transverse movement. Meansalso is` included to hold the plate against longitudinal movement. Suchmeans comprises a nub J8 near each end of the tube and at an end of theplate 2l. Said nubs are formed by locally heating the tube at thedesired regions until the tube softens and then indenting the tube witha blunt rounded point. This operation is perfumed after the plate is inthe tube and the nubs thus are pressed against the ribbons 22.

The characters are provided by forming shallow depressions 2l of properoutline in the plate 28 and filling the depressions with a fluorescentmaterial 40. The depressions are fashioned in any suitable manner, forinstance by sand-blasting through a. stencil, chemical etching,photoengraving or molding when the plate is made.

Over the area of the plate thus treated there is applied, asby',brushing or spraying, fluorescent powders in suspension in avarnish, lacquer or other suitable iluid carrier of the type commonlyused for the application of such powders on glass tubes. If desired,powders of different composition can be employed on different areas ofthe plate in order to obtain differently colored characters when thetube is activated. After the carrier is dry, the front surface of theplate is scraped with 9. straight edge to remove all fluorescentf powderexcept that inside the depressions. Then the plate is heated tovolatilize the solidified carrier, as is done in the manufacture offluorescent lamps. By way of example, a sat isfactory depth for thedepressions is about 0.5 mm. It will be apparent that the formation ofthe characters is carried out before insertion of the plate in the tube.

It is desired to point out that, when the depressions are formed byactual removal of portions of the plate, i. e. by etching, the surfaceto which the powders are applied can be thoroughly cleaned and there isno likelihood that the powders will fall of! during use, as now often isthe case, because the surfaces to which the powders are applied cannotbe kept perfectly clean while manufacturing the plate.

It may be mentioned that the' sequence of steps in the assembly of thesign is to insert the prepared and wrapped plate in the tube, place therings in posit on, form the nubs, insert the electrodes, form t e stems,evacuate the tube, charge the tube, close the stub, connect theterminals, apply the shells, and mount the terminals.

In Fig. 6 I have shown a fluorescent sign lamp l2 which is similar inall respects to the lamp I0 except for the means to hold the characterplate against transverse movement. All parts identical u with parts ofthe lamp I0 are denoted by the same andere 5 a reference numeralsprimed. The plate Il' ishcld might be made in the embodiments above setagainst transverse movement by a ltwo-,ended forth, it is to beunderstood that all matter herein compression spring 4| having a loop 4linterdescribed, or shown in the accompanying drawmediate its ends.Refractory beads 4l. 50, e. g. ings, is to be interpreted asillustrative and not ceramic beads, are mounted on the ends of the 5. ina limiting sense.

spring.l One bead bears againstthe inner sur- Having thus described myinvention, I claim face of the tube l2'- and the other against the asnewand desire tosecure by Letters Patent: plate 2l', the latter beadpressing either directly l. A fluorescent sign lamp comprising a sealedagainst the plate or engaging the ribbon 32'. To elongated transparenttube, electrodes adjacent hold the spring in place, the tube I2 isheated 10 opposite ends of said tube, a charge of attenuated in theregion of the bead 4B. When the tube gas in said tube, a plate in saidtube, said plate softens slightly this bead will push out the wallhaving fluorescent characters on a surface therea short distance to forma depression 52 in which 0f, the width of said plate being less than thethe bead 48 remains seated. major cross-sectional dimension of the tube.and The foregoing plete mountinss are resilient: is means to locate saidplate in a position onset however, in accordance with another aspect offrom the eeuu-9,1 longitudinal axis of the tube myinvention thecharacter nleteisrisidlymvuntwith its character-carrying surfaceextending ed, this form of the invention being illustrated lengitudmeuyof the tube and radially spaced in F18 7 wherein all Darts Similar 150those 0f from said axis and the opposite surface of the the lamp Itaredenoted by the same reference n plete disposed en the seme side ofthe exis end numerals double primed. The sign Il shown epeeed furthertherefrom, in F18- '7 has its 5ba-meter P1te n" held in 03:' 2.Afiuorescent lamp S1811 as set forth in claim eet position by e Deir ofmeuntin members it i wherein the locating means composee e, resilone ateach end o! the plate. Each such memgent member undercompressione-between the bei @Prises a Small rod u hvm *im 25character-carrying surface of the plate and the arms 8l. B2 on an endthereof, so that the memewue wen ef the tube, bei' i8 approximately inthe Shape 0f 9' Y o. 3. A iluorescent lamp sign as set forth in claimthe rod s., i. e. the of the Y, 110ml 18 1 wherein the means comprises aresuprovided which engages or nts into a correspondgent member undercompl-essieu between the mg nomh on the end edge 0f the 30 cmwtermingsurface of the and 2|", s0 that, two ends thus Supported, the wan of thetube and a cushioning plete is rigidly held 1n the tube- T keep theciment disposed between the opposite mfaee members in place, each of theend of of the and the adjant wan of the tube. the Y is fashioned anmdentauon wm 4. A nuorescent as set forth in the wan 0f the after forinstan@ u 1 wherein me means comprises a spring by the application ofheat, is pushed. the result- ,me under mmm-essieu between thecharacteringconnguration Clearly mmctedinm- 7. um mfm of the and theopl-site lfdesiredathinplyofasbestosorslasswool mefthetube,

ribbon may be inserted between the members It P50170 ammo. and ends oi'the plate 28" to discourage rocking 40 of the plate. It will be observedthat in this form REFERENCES CITED of my invention the character platedoes not touch the tube and accordingly it is not necessary to interposeany cushioning element between me d um mnt' um plate and tube, .u UNITEDSTATES PATENTS It thus will be seen that I have provided signs NumberName Date which achieve the several objects of my invention 3,113,000Wojtkowiak MIIU 17. 1938 and are well adapted to meet the conditions of3,177,710 Gordon Oct. 31. 1939 practical use. 2,335,712 Price Dec. 24.1040 Asvarious possible embodiments mizht bemadc I0 3,373,127 Noel Feb3. i942 of the above invention, and as various changes 3,430,534 xeniumet a1. Aug: a0, 1949 The following references are of record in the

